Nitration of aniline with a mixture of conc. HNO3 and conc. H2SO4 gives a substantial proportion of the meta-nitro product. The reason is that

aniline is largely converted into anilinium ion, whose -NH3+ group is a meta-directing group

the -NH2 group is itself a meta director

the nitronium ion attacks only the nitrogen

aniline is oxidised to benzoic acid before nitration

aniline is largely converted into anilinium ion, whose -NH3+ group is a meta-directing group

JEE Advanced levelSingle correct optionDifficulty 3 of 3g2104

Nitration of aniline with a mixture of conc. $HNO X_{3}$ and conc. $H X_{2} SO X_{4}$ gives a substantial proportion of the meta-nitro product. The reason is that

Athe $- NH X_{2}$ group is itself a meta director
Bthe nitronium ion attacks only the nitrogen
Caniline is oxidised to benzoic acid before nitration
Daniline is largely converted into anilinium ion, whose $- NH X_{3} X^{+}$ group is a meta-directing group

In the strongly acidic medium the basic amino group (pKaH of anilinium 4.6) is protonated to

- NH X_{3} X^{+}

, which is strongly electron-withdrawing (

- I

, no lone pair) and meta-directing. Part of the aniline remains free and gives ortho/para products, so a mixture results.